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What Causes Climate Change

It is a concern that the climatic changes occurring today have been speeded up because of man's activities.

The natural variability and the climate fluctuations of the climate system have always been part of the Earth’s history. However, there have been changes in concentrations of greenhouse gases in the atmosphere growing at an unprecedented rate and magnitude therefore as a human race we must act now to stabilise and arrest further changes.

Climate change can be divided into two categories, human and natural causes.
 

Human causes

"It has been demonstrated beyond reasonable doubt that the climate is changing due to man-made greenhouse gases. We are already committed to future substantial change over the next 30 years and change is likely to accelerate over the rest of the 21st century."
 

The Met Office, Hadley Centre, UK
 

"The Hadley Centre holds an unique position in the world of climate science. No other single body has a comparable breadth of climate change science and modelling, or has made the same contribution to global climate science and current knowledge."

Independent Review 2007

The Industrial Revolution in the 19th century saw the large-scale use of fossil fuels for industrial activities. Fossil fuels such as oil, coal and natural gas supply most of the energy needed to run vehicles, generate electricity for industries and households. The energy sector is responsible for about ¾ of the carbon dioxide emissions, 1/5 of the methane emissions and a large quantity of nitrous oxide.

Carbon dioxide is undoubtedly, the most important greenhouse gas in the atmosphere. Changes in land use pattern, deforestation, land clearing, agriculture, and other activities have all led to a rise in the emission of carbon dioxide. Methane is another important greenhouse gas in the atmosphere. It is released from animals such as dairy cows, goats, pigs, buffaloes, camels, horses and sheep Methane is also emitted during the process of oil drilling, coal mining, leaking gas pipelines, landfills and waste dumps.

The certainty of global warming can be seen through some of the natural phenomenon like the effect on crops and extreme weather conditions around the world. It is especially clear in the dramatic change of the polar caps, i.e. the Arctic ice cap is shrinking and the Antarctica ice shelf is melting.

 

Natural causes

The earth’s climate is influenced and changed through natural causes like volcanic eruptions, ocean current, the earth’s orbital changes and solar variations.

Volcanic eruptions - When a volcano erupts it throws out large volumes of sulphur dioxide (SO2), water vapour, dust, and ash into the atmosphere. Large volumes of gases and ash can influence climatic patterns for years by increasing planetary reflectivity causing atmospheric cooling.

Ocean current - The oceans are a major component of the climate system. Ocean currents move vast amounts of heat across the planet. Winds push horizontally against the sea surface and drive ocean current patterns. Interactions between the ocean and atmosphere can also produce phenomena such as El Niño which occur every 2 to 6 years. Deep ocean circulation of cold water from the poles towards the equator and movement of warm water from the equator back towards the poles. Without this movement the poles would be colder and the equator warmer. The oceans play an important role in determining the atmospheric concentration of CO2. Changes in ocean circulation may affect the climate through the movement of CO2 into or out of the atmosphere.

Earth orbital changes - The earth makes one full orbit around the sun each year. It is tilted at an angle of 23.5° to the perpendicular plane of its orbital path. Changes in the tilt of the earth can lead to small but climatically important changes in the strength of the seasons, more tilt means warmer summers and colder winters; less tilt means cooler summers and milder winters. Slow changes in the Earth’s orbit lead to small but climatically important changes in the strength of the seasons over tens of thousands of years. Climate feedbacks amplify these small changes, thereby producing ice ages.

Solar variations - The Sun is the source of energy for the Earth’s climate system. Although the Sun’s energy output appears constant from an everyday point of view, small changes over an extended period of time can lead to climate changes. Some scientists suspect that a portion of the warming in the first half of the 20th century was due to an increase in the output of solar energy.